Answering why one turtle is female and another male


Thea Gessler examines the epigenetics of sex determinationSex chromosomes at the time of fertilization determines the sex of most snakes and lizards. But, the sex of most turtles is determined by environmental conditions after fertilization.

For turtles with temperature-dependent sex determination, the temperature during certain points in development determine the sex ratio. Usually low temperatures produce male turtles and high temps result in more females. A theoretical pivotal temperature range produces a 50/50 sex ratio.

Thea Gessler intends to examine egg yolks produced at this pivotal temperature to determine what other factors might play into sex determination. She will specifically study the RNA deposited in the yolk by the mother.

A graduate of Concordia College and native Minnesotan, Gessler chose to pursue a Ph.D. in genetics and genomics at Iowa State University. Gessler joined Nicole Valenzuela's lab because of her interest in evolutionary biology and the epigenetics of sex determination. But she also enjoyed the camaraderie.

"The lab is very collaborative and we all get along really well."

In her spare time, Gessler enjoys cross country skiing, gardening, reading, and "watching way too much Netflix." She's also experienced both the polar night and midnight sun during a trip above the Arctic circle in Norway.